做了四年的JavaEE开发，用了hibernate四年，今天才知道，原来还可以把HQL语句或SQL语句写在Hibernate实体类对应的映射文件中的。
打开Hibernate的Session的源码，我们可以看到有一个getNamedQuery(String name);的方法，如下：
/** * Obtain an instance of <tt>Query</tt> for a named query string defined in the * mapping file. * * @param queryName the name of a query defined externally * @return Query * @throws HibernateException */ public Query getNamedQuery(String queryName) throws HibernateException;
这个方法就是可以执行定义在Hibernate实体类映射文件中的HQL或Sql语句。
具体做法下面我一一讲解，首先测试在映射文件中定义HQL语句。
我在User实体类的映射文件中定义了一个name为getUserByName的HQL查询语句，代码如下：
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.xigua.domain"> <class name="User"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="birthday"/> </class> <!-- 定义一个查询，名称为getUserByName --> <query name="getUserByName"> <![CDATA[from User where name = :name]]> </query> </hibernate-mapping>
然后编写测试类使用Session中的getNamedQuery(String name)方法进行测试，代码如下：
package com.xigua.test;
import java.util.Date;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;
public class Test9 {
public static void main(String[] args) {
addUser();
String name = "xigua";
List<User> list = namedQuery(name);
if(list != null && !list.isEmpty()) {
for(User user : list) {
System.out.println(user.getId() + ", " + user.getName() + ", " + user.getBirthday());
}
}
}
public static void addUser() {
Session session = null;
Transaction tx = null;
try{
session = HibernateUtil.getSession();
tx = session.beginTransaction();
User user = new User();
user.setName("xigua");
user.setBirthday(new Date());
session.save(user);
user = new User();
user.setName("donggua");
user.setBirthday(new Date());
session.save(user);
tx.commit();
} catch(Exception e) {
if(tx != null) {
tx.rollback();
}
} finally {
if(session != null) {
session.close();
}
}
}
public static List<User> namedQuery(String name) {
Session session = null;
try{
session = HibernateUtil.getSession();
Query query = session.getNamedQuery("getUserByName");
query.setParameter("name", name);
return query.list();
}catch(Exception e) {
e.printStackTrace();
} finally {
if(session != null) {
session.close();
}
}
return null;
}
}
注意红色部分代码。
在映射文件中除了可以定义HQL语句，也还是可以定义Sql语句的。
前面的User实体类的映射文件修改如下：
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.xigua.domain"> <class name="User"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="birthday"/> </class> <!-- 定义一个查询，名称为getUserByName <query name="getUserByName"> <![CDATA[from User where name = :name]]> </query> --> <sql-query name="getUserByName"> <![CDATA[select id, name from user where name = :name]]> </sql-query> </hibernate-mapping>
测试代码如下：
package com.xigua.test;
import java.util.Date;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;
public class Test10 {
public static void main(String args[]) {
addUser();
String name = "xigua";
User user = namedSqlQuery(name);
if(user != null) {
System.out.println(user.getId() + ", " + user.getName());
}
}
public static void addUser() {
Session session = null;
Transaction tx = null;
try{
session = HibernateUtil.getSession();
tx = session.beginTransaction();
User user = new User();
user.setName("xigua");
user.setBirthday(new Date());
session.save(user);
user = new User();
user.setName("donggua");
user.setBirthday(new Date());
session.save(user);
tx.commit();
} catch(Exception e) {
if(tx != null) {
tx.rollback();
}
} finally {
if(session != null) {
session.close();
}
}
}
public static User namedSqlQuery(String name) {
Session session = null;
try{
session = HibernateUtil.getSession();
Query query = session.getNamedQuery("getUserByName");
query.setParameter("name", name);
Object[] obj = (Object[]) query.uniqueResult();
if(obj != null) {
User user = new User();
user.setId(Long.valueOf(obj[0].toString()));
user.setName(obj[1].toString());
return user;
}
}catch(Exception e) {
e.printStackTrace();
} finally {
if(session != null) {
session.close();
}
}
return null;
}
}
映射文件中还有些其它的配置，暂时还没具体搞懂，比如下面红色的代码：
<sql-query name="getUserByName"> <![CDATA[select id, name from user where name = :name]]> <query-param name="name" type="string"/> <return></return> <return-join alias="" property=""></return-join> <return-scalar column=""/> <synchronize table=""/> </sql-query>
还有一点像说明的是<query>跟<sql-query>的配置是可以放到<class>节点里面的。
我现在是放在<class>节点外面，表示全局可用，这里需要注意不要跟其它映射文件中定义的<query>或<sql-query>同名。
如果将<query>或<sql-query>放在<class>节点里面，在java代码中使用的时候需要将package名跟class名都写上，具体见下面配置的映射文件代码跟测试代码。
映射文件代码：
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.xigua.domain"> <class name="User"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="birthday"/> <!-- 定义一个查询，名称为getUserByName (这里将<query>放到<class>节点里面来)--> <query name="getUserByName"> <![CDATA[from User where name = :name]]> </query> </class> </hibernate-mapping>
java测试代码（注意下图红色部分字符串）
package com.xigua.test;
import java.util.Date;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;
public class Test9 {
public static void main(String[] args) {
addUser();
String name = "xigua";
List<User> list = namedQuery(name);
if(list != null && !list.isEmpty()) {
for(User user : list) {
System.out.println(user.getId() + ", " + user.getName() + ", " + user.getBirthday());
}
}
}
public static void addUser() {
Session session = null;
Transaction tx = null;
try{
session = HibernateUtil.getSession();
tx = session.beginTransaction();
User user = new User();
user.setName("xigua");
user.setBirthday(new Date());
session.save(user);
user = new User();
user.setName("donggua");
user.setBirthday(new Date());
session.save(user);
tx.commit();
} catch(Exception e) {
if(tx != null) {
tx.rollback();
}
} finally {
if(session != null) {
session.close();
}
}
}
public static List<User> namedQuery(String name) {
Session session = null;
try{
session = HibernateUtil.getSession();
Query query = session.getNamedQuery("com.xigua.domain.User.getUserByName");
query.setParameter("name", name);
return query.list();
}catch(Exception e) {
e.printStackTrace();
} finally {
if(session != null) {
session.close();
}
}
return null;
}
}